[Role of miR-21 in rat hepatic oval cell proliferation and activation].

Objective To investigate the possible mechanisms of miR-21-mediated regulation of proliferation and activation of hepatic oval cells.Methods The 2-acetamidofluorene/partial hepatectomy (2-AAF/PH) method was applied to generate hepatic oval cell activation model in male Sprague-Dawley rats; after the 7 days of 2-AAF/PH or PH alone (control),the rats were sacrificed at 0 h,6 h,12 h,24 h,72 h and 168 h.Expression of miR-21 was detected by real-time PCR and differences between groups were evaluated using the two-sample t-test.Differential transcription of miR-21 target genes was assessed bioinformatically,and with western blotting to detect changes in protein expression of the target gene.Results The rat hepatic oval cell activation model was successfully established.The 2-AAF/PH rats showed miR-21 expression beginning to increase at 12 h,peaking at 24 h,and decreasing thereafter until an increase at 168 h.For the control group,the miR-21 expression began to increase at 6 h,until 24 h when expression began steadily declining to reach the original level.Compared to the control group,the experimental group showed expression of miR-21 that was significantly less at 6 h (P =0.039,t =3.029) and significantly more at 24 h and 168 h (P =0.026,t =-3.433 andP =0.007,t =-5.105).Among the predicted target genes of miR-21 were WW domain containing E3 ubiquitin protein ligase 1 (WWD),Smad family member 7 (Smad7),and polybromo-1 (Pbrm1).Smad7 protein expression began to decrease at 6 h in the control group,until reaching its minimum at 24 h when it increased; in the experimental group,SMAD7 expression increased at 6 h,then began to decrease with the minimum detected at 168 hour.In the control group,the Smad7 mRNA expression decreased slightly at 6 h,then began to increase,reaching its peak at 24 h when the expression fell to the original level.In the experimental group,the Smad7 mRNA expression began to increase at 6 h and reached its peak at 24 h when it decreased; the expression was little more than its original level at 168 h.Smad7 protein expression was negatively correlated with miR-21,and Smad7 mRNA expression was positively correlated with miR-21 but negatively correlated with Smad7 protein expression.Conclusion miR-21 may play a vital role in the activation and proliferation of hepatic oval cells.As a target gene of miR-21,Smad7 might be involved in the process. Key words: Cell proliferation;  MicroRNA-21;  Hepatic oval cell;  Cell activation